1. Field of the Invention
The present invention relates to a disk storage device for magnetically recording and reproducing information, and more particularly to a technique to maintain a slider at a low flying height thereby achieving a high-capacity magnetic disk storage device capable of operating at a high speed.
2. Description of the Related Art
A typical magnetic head supporting mechanism which is practically used in a magnetic disk storage device is disclosed for example in JP-A-55-22296 (1980). In this technique, a magnetic head is mounted on a slider, and the slider is fixed to a gimbal with an adhesive or the like via the entire contact area between the slider and a flap of the gimbal. The gimbal is flexible in the direction perpendicular to the disk surface so that the slider may move above the disk maintaining a correct distance between the slider and disk surface. The gimbal is provided with a protrusion called a dimple so that the slider can rotate about the vertex of the dimple. A load arm includes a rigid portion for supporting the gimbal and a spring for applying a proper load to the slider via the dimple.
JP-A-54-133312 (1979) discloses a magnetic head supporting mechanism for use in a floppy disk storage device. In this magnetic head supporting mechanism a movable base plate is supported in a rotatable fashion by a fixed base plate, and a gimbal is connected to an end of the fixed base plate and also to an end of the movable base plate. A magnetic head is fixed to the gimbal in such a manner that the upper surface of the magnetic head is bonded via an adhesive or the like to the central part of the gimbal. Furthermore, the center of the back surface of the gimbal is supported by a supporting pin in such a manner as to suppress the fluctuation of the magnetic head in directions perpendicular to the disk surface and apply a proper load to a slider.
In another example disclosed in JP-A-1-179287 (1989), a gimbal is formed with four arms disposed in radial directions. Of these arms, ends of two arms which are not adjacent to each other are fixed to a slider, and ends of the remaining two arms are fixed to a load arm, thereby forming a head supporting mechanism. A spacer is disposed between the gimbal and the slider or otherwise a groove is formed on the surface of the slider to which the gimbal is attached so that the slider can have a proper degree of flexibility.
In a head supporting mechanism disclosed in JP-A-55-22296 (1980), a slider is fixed to a gimbal with an adhesive or the like via the entire contact area between the slider and a flap of the gimbal. In this structure, the slider is deformed due to warping or twisting which initially exists in the flap of the gimbal when the gimbal is produced, or due to warping or twisting which occurs in the flap of the gimbal due to the stress arising when the slider is bonded to the flap or due to a loading force or an external disturbance. The above deformation of the slider results in warping or twisting of the air bearing surface of the slider, and thus produces a variation in the flying height of the slider. Furthermore, the flap is influenced by the warping or twisting which initially exists in the flap of the gimbal when the gimbal is produced, or due to warping or twisting which occurs in the flap of the gimbal due to the stress arising when the slider is bonded to the flap or due to a loading force or an external disturbance. The above influence creates a variation in the initial static attitude of the slider, and thus a variation in the flying height of the slider. If the flying height of the slider becomes less than a designed value, a possibility occurs that the slider comes in contact with a disk and data is lost. Therefore, it is impossible to reduce the flying height to a level low enough to further increase the recording density. This has been an obstacle to realization of a high-capacity magnetic disk storage device. The slider which is located at an end of a load arm is pressed against the disk surface by the load arm via a dimple. However, if the gimbal is deformed in a lateral direction or a direction along the disk surface during a seeking operation or when an uncontrollable condition occurs, slipping of the dimple occurs. The dimple will be held at the slipped position by a frictional force applied to the dimple, and thus a positional error occurs between the slider and the load arm. As a result, each head of a plurality of head supporting mechanisms has a positional error. In the case of a dedicated servo method, the above positional error results in an insufficient positioning accuracy, while in the case of an embedded servo method, it is needed to correct the position of each of the plurality of heads, which causes a delay in access time.
Also in a magnetic head supporting mechanism disclosed in JP-A-54-133312 (1979), the entire upper surface of a slider is fixed to a gimbal, and therefore, warping or twisting occurs between the gimbal and the slider, which causes variations in flying height. Thus, it is impossible to achieve a high-capacity magnetic disk storage device. Furthermore, since a supporting pin is in contact with the gimbal, the deformation of the gimbal causes a head to be shifted in position via a frictional force as in JP-A-55-22296 (1980). In a floppy disk storage device, only one disk and two or less magnetic disks are used. Therefore, the shifting of the head position does not lead to a serious delay in access time. However, in the case of a magnetic disk storage device which includes a plurality of disks and ten or more magnetic heads, the shifting of the head position produces serious problems.
In a head supporting mechanism disclosed in JP-A-1-179287 (1989), in addition to the problems associated with warping and twisting as in the above examples, there are further problems as described below. That is, the surface of a gimbal to which a slider is attached is divided into two pieces, and these two pieces are pulled to each other due to a pressing load applied to the slider, which causes the air bearing surface of the slider to be warped. In particular, the twisting between the slider fixing surfaces imposes a great influence. In this example, since there is no dimple in a sliding part, the positional shifting of a head does not occur. However, the absence of the dimple results in an absence of damping due to friction, which in turn results in a great amplitude of vibration. As a result, it is difficult to achieve high positioning accuracy.